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      1 /*
      2  * Copyright 2006 The Android Open Source Project
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #ifndef SkColorFilter_DEFINED
      9 #define SkColorFilter_DEFINED
     10 
     11 #include "SkBlendMode.h"
     12 #include "SkColor.h"
     13 #include "SkFlattenable.h"
     14 #include "SkRefCnt.h"
     15 
     16 class GrContext;
     17 class GrFragmentProcessor;
     18 class SkArenaAlloc;
     19 class SkBitmap;
     20 class SkColorSpace;
     21 class SkColorSpaceXformer;
     22 class SkRasterPipeline;
     23 
     24 /**
     25  *  ColorFilters are optional objects in the drawing pipeline. When present in
     26  *  a paint, they are called with the "src" colors, and return new colors, which
     27  *  are then passed onto the next stage (either ImageFilter or Xfermode).
     28  *
     29  *  All subclasses are required to be reentrant-safe : it must be legal to share
     30  *  the same instance between several threads.
     31  */
     32 class SK_API SkColorFilter : public SkFlattenable {
     33 public:
     34     /**
     35      *  If the filter can be represented by a source color plus Mode, this
     36      *  returns true, and sets (if not NULL) the color and mode appropriately.
     37      *  If not, this returns false and ignores the parameters.
     38      */
     39     virtual bool asColorMode(SkColor* color, SkBlendMode* bmode) const;
     40 
     41     /**
     42      *  If the filter can be represented by a 5x4 matrix, this
     43      *  returns true, and sets the matrix appropriately.
     44      *  If not, this returns false and ignores the parameter.
     45      */
     46     virtual bool asColorMatrix(SkScalar matrix[20]) const;
     47 
     48     /**
     49      *  If the filter can be represented by per-component table, return true,
     50      *  and if table is not null, copy the bitmap containing the table into it.
     51      *
     52      *  The table bitmap will be in SkBitmap::kA8_Config. Each row corresponding
     53      *  to each component in ARGB order. e.g. row[0] == alpha, row[1] == red,
     54      *  etc. To transform a color, you (logically) perform the following:
     55      *
     56      *      a' = *table.getAddr8(a, 0);
     57      *      r' = *table.getAddr8(r, 1);
     58      *      g' = *table.getAddr8(g, 2);
     59      *      b' = *table.getAddr8(b, 3);
     60      *
     61      *  The original component value is the horizontal index for a given row,
     62      *  and the stored value at that index is the new value for that component.
     63      */
     64     virtual bool asComponentTable(SkBitmap* table) const;
     65 
     66     void appendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*, bool shaderIsOpaque) const;
     67 
     68     enum Flags {
     69         /** If set the filter methods will not change the alpha channel of the colors.
     70         */
     71         kAlphaUnchanged_Flag = 1 << 0,
     72     };
     73 
     74     /** Returns the flags for this filter. Override in subclasses to return custom flags.
     75     */
     76     virtual uint32_t getFlags() const { return 0; }
     77 
     78     /**
     79      *  If this subclass can optimally createa composition with the inner filter, return it as
     80      *  a new filter (which the caller must unref() when it is done). If no such optimization
     81      *  is known, return NULL.
     82      *
     83      *  e.g. result(color) == this_filter(inner(color))
     84      */
     85     virtual sk_sp<SkColorFilter> makeComposed(sk_sp<SkColorFilter>) const { return nullptr; }
     86 
     87     SkColor filterColor(SkColor) const;
     88     SkColor4f filterColor4f(const SkColor4f&) const;
     89 
     90     /** Create a colorfilter that uses the specified color and mode.
     91         If the Mode is DST, this function will return NULL (since that
     92         mode will have no effect on the result).
     93         @param c    The source color used with the specified mode
     94         @param mode The blend that is applied to each color in
     95                         the colorfilter's filterSpan[16,32] methods
     96         @return colorfilter object that applies the src color and mode,
     97                     or NULL if the mode will have no effect.
     98     */
     99     static sk_sp<SkColorFilter> MakeModeFilter(SkColor c, SkBlendMode mode);
    100 
    101     /** Construct a colorfilter whose effect is to first apply the inner filter and then apply
    102      *  the outer filter to the result of the inner's.
    103      *  The reference counts for outer and inner are incremented.
    104      *
    105      *  Due to internal limits, it is possible that this will return NULL, so the caller must
    106      *  always check.
    107      */
    108     static sk_sp<SkColorFilter> MakeComposeFilter(sk_sp<SkColorFilter> outer,
    109                                                   sk_sp<SkColorFilter> inner);
    110 
    111     /** Construct a color filter that transforms a color by a 4x5 matrix. The matrix is in row-
    112      *  major order and the translation column is specified in unnormalized, 0...255, space.
    113      */
    114     static sk_sp<SkColorFilter> MakeMatrixFilterRowMajor255(const SkScalar array[20]);
    115 
    116     /** Construct a colorfilter that applies the srgb gamma curve to the RGB channels */
    117     static sk_sp<SkColorFilter> MakeLinearToSRGBGamma();
    118 
    119     /** Construct a colorfilter that applies the inverse of the srgb gamma curve to the
    120      *  RGB channels
    121      */
    122     static sk_sp<SkColorFilter> MakeSRGBToLinearGamma();
    123 
    124 #if SK_SUPPORT_GPU
    125     /**
    126      *  A subclass may implement this factory function to work with the GPU backend. It returns
    127      *  a GrFragmentProcessor that implemets the color filter in GPU shader code.
    128      *
    129      *  The fragment processor receives a premultiplied input color and produces a premultiplied
    130      *  output color.
    131      *
    132      *  A null return indicates that the color filter isn't implemented for the GPU backend.
    133      */
    134     virtual sk_sp<GrFragmentProcessor> asFragmentProcessor(GrContext*,
    135                                                            SkColorSpace* dstColorSpace) const;
    136 #endif
    137 
    138     bool affectsTransparentBlack() const {
    139         return this->filterColor(0) != 0;
    140     }
    141 
    142     SK_TO_STRING_PUREVIRT()
    143 
    144     SK_DECLARE_FLATTENABLE_REGISTRAR_GROUP()
    145     SK_DEFINE_FLATTENABLE_TYPE(SkColorFilter)
    146 
    147 protected:
    148     SkColorFilter() {}
    149 
    150     sk_sp<SkColorFilter> makeColorSpace(SkColorSpaceXformer* xformer) const {
    151         return this->onMakeColorSpace(xformer);
    152     }
    153     virtual sk_sp<SkColorFilter> onMakeColorSpace(SkColorSpaceXformer*) const {
    154         return sk_ref_sp(const_cast<SkColorFilter*>(this));
    155     }
    156 
    157 private:
    158     /*
    159      *  Returns 1 if this is a single filter (not a composition of other filters), otherwise it
    160      *  reutrns the number of leaf-node filters in a composition. This should be the same value
    161      *  as the number of GrFragmentProcessors returned by asFragmentProcessors's array parameter.
    162      *
    163      *  e.g. compose(filter, compose(compose(filter, filter), filter)) --> 4
    164      */
    165     virtual int privateComposedFilterCount() const { return 1; }
    166 
    167     virtual void onAppendStages(SkRasterPipeline*, SkColorSpace*, SkArenaAlloc*,
    168                                 bool shaderIsOpaque) const = 0;
    169 
    170     friend class SkColorSpaceXformer;
    171     friend class SkComposeColorFilter;
    172 
    173     typedef SkFlattenable INHERITED;
    174 };
    175 
    176 #endif
    177